Best Sweet Potato Souffle Casserole

Name: Best Sweet Potato Souffle Casserole
Ingredients: 2 pounds sweet potatoes (firm skin, no soft spots, deep orange color); 6 tablespoons unsalted butter (European-style for richer flavor); 0.5 cup heavy cream (36% fat minimum); 0.5 cup light brown sugar (soft, clump-free); 2 large eggs (room temperature); 1 teaspoon ground cinnamon (Vietnamese cinnamon preferred); 0.25 teaspoon baking powder (fresh, less than 6 months old); 0.75 cup toasted pecans (fresh, not rancid); 0.25 cup light brown sugar (for topping); 3 tablespoons all-purpose flour (unbleached preferred); 3 tablespoons unsalted butter (melted for topping)